Process and device for preparing and/or extracting samples using a vaporizable agent at high temperature

ABSTRACT

A process for preparing and/or extracting samples by heating them together with a solvent in a container under pressure, using a Soxhlet apparatus. The samples are dried by heating in a container; and the resultant vapors are drawn off to generate a vacuum in the container.

This application is a national stage application filed under 371 ofPCT/EP95/01081.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an improved process and apparatus from which asample is extracted under conditions of high temperature and highpressure.

2. Description of the Related Art

It is known that an extractor of the type known as 10 Soxhlet can beused for the multiple extraction of samples, whereby the solvent can bedistilled off and the desired substance(s) can be extracted from thesample in a continuous cycle.

There are such devices in which the distillation and extraction takeplace at normal (ambient) pressure or at elevated pressure(high-pressure extraction).

A device of the above referred to type is familiar as a one-piece glassmolded article, which consists of an upper glass flask for the samplesand a lower glass flask for the solvent, and two separate externalconnection tubes that connect the lower and upper glass flasks together.One of the connection tubes is a vapor tube, which branches off from thelower glass flask and leads into the upper glass flask near the topthereof. The other connection tube is an overflow tube which starts fromthe lower part of the upper glass flask, extends upwards in it up to acertain level, and then leads down into the lower glass flask.

This known device is expensive, in relation both to its construction andto the procedures that can be carried out with it. Heating of both thesolvent and the sample material is difficult, firstly because the heatfrom a heat source, for example a Bunsen burner, is not easy to transferto the materials being heated, and then because glass, as a constructionmaterial, is a poor conductor of heat. As a rule, this known device isonly made in relatively small sizes, so that only small extraction jobscan be carried out. A further disadvantage of the known device is thatsince it is made of glass, it is very sensitive and can break easily.

A high-pressure extraction device is described in USA 4 265 860 or in DEA1 4 114 525.9. In this known device the extractor is housed in apressure-tight housing with a charging opening closed off by a cover.During operation of the device, distillation of the solvent increasesthe pressure in the pressure vessel, which causes the boiling point ofthe solvent to rise and so increases the working temperature. Thissubstantially enhances the performance of the device, and in additionthe elevated pressure favors the extraction of the samples because thesolvent can penetrate better into the sample material.

In addition, in the device known from DE,A1, 4 114 525.9, tworeceptacles are provided in the pressure vessel, namely one solventcontainer made of plastic lining the inner wall of the metal pressurevessel, and inside and concentric with that, a glass sample containerresting on a shoulder and fitted with an external overflow pipeconnected in one piece with the sample container. The sample containeris arranged a certain distance above the bottom of the solventcontainer, supported by a circular flange that rests against an interiorshoulder of the solvent container. The solvent and sample materials areheated by microwave radiation admitted via an opening at the bottom ofthe pressure vessel covered by a material transparent to microwaves.When the solvent evaporates, the vapor passes upwards into the annularspace between the solvent container and the sample container, andthrough holes in the circular flange into the vapor space over thesample container. In the area of the vapor space, the pressure vessel issurrounded by a cooling device formed by an annular water pipe in theperipheral wall of the pressure vessel and therefore in direct contactwith the upright wall thereof. Over the sample container is a perforatedscreen over which the solvent condensed by the cooling device againstthe upright inner wall flows and falls into the sample container.

In WO 93 22650 devices for the vaporization or drying and extraction ofsamples are described in several design variants (see FIGS. 1 to 23). Inthese design examples, the inside of at least one container forreceiving and treating the sample is connected to a suction device bymeans of one suction pipe, and by means of a common or two separateinlet pipes to a flushing gas supply device and/or a supply device for areagent or solvent. During the vaporization treatment, the vapors givenoff when the sample is heated are continually extracted by the suctiondevice, producing an underpressure in the container which lowers theboiling and evaporation points of the reagent, so that the sample can betreated at a lower temperature. This is especially advantageous when thesample material and/or the reagent medium must not be treated at highertemperatures, which they may not tolerate for example.

FIG. 24 of this specification shows a device for the preparation ofsamples under the action of heat and elevated pressure.

SUMMARY OF THE INVENTION

The object of the invention is to develop the process and the equipmentfurther, in such a way as to enable more rational treatment of thesamples.

In the process according to the invention, a sample is not onlyextracted under elevated pressure, but also, before and/or after itspreparation and/or extraction, it is dried under reduced pressure. Thisachieves the desired rational and simple procedure, allowing accurateanalysis of the sample and determination of its constituents, sincelargely accurate measurement values can be obtained and faultymeasurements avoided. The device of the invention is also constructedsimply and can be operated conveniently, rapidly and safely.

In both of the previously known devices, the formation of solvent vaporis prejudiced. In the first of the known devices described, the vapormust first flow through an external tube with a relatively smallinternal cross-15 section, and then through an external cooling zone. Inthe second of the known devices described, the vapor flow is impeded bythe overflow pipe. Furthermore, both of the known designs are sensitiveand fragile.

A further development of the invention confers the advantage that vaporflow will be improved while guaranteeing a simple structure.

In this further development, the overflow duct is integrated as a grooveor channel in the body or wall of the sample container. Thus, theoverflow duct is no longer in the way of the vapor flow and this alsomakes for a smaller, compact and robust structure, since there is noprojecting pipe that could be broken or damaged.

By means of the further development, the heating of the solvent and/orthe sample material is improved, and in addition, solvents can be usedwhich do not absorb microwaves. In this further development, the solventand/or sample material are if necessary additionally heated indirectly,considerably reducing the operation time and improving the performance.

According to another development of the invention, a simple structureinexpensive to manufacture is achieved, which guarantees safety androbustness. In this further development, the pressure vessel is at thesame time the container for the solvent, whereby a further importantsimplification is achieved since no connection aperture need be providedand simpler and more effective coupling is guaranteed.

The further development of this invention improves the cooling orformation of condensate. In this further development, the cooling deviceis arranged in the area of the cover of the pressure vessel. This notonly avoids any weakening of the pressure vessel walls, but since thecover acts as the support of the cooling device, the said device can bemore simply and cheaply arranged, attached or formed on it.

By means of a still further development, a simple and robust structureis guaranteed while allowing the sample container to be introduced intoor removed from the pressure vessel from above. The sample containerstands on a preferably central and bar-shaped pedestal which makespossible the arrangement of the chamber for the medium underneath thesample container.

Other further developments according to the invention confercharacteristics that contribute to solving the problem of simplifyingthe structure and making it more compact, so that the capacity of thepressure vessel can be enlarged, the number of components reduced, thefunction improved and made safer, and the structure is also less costly.

BRIEF DESCRIPTION OF THE DRAWINGS

In what follows, the invention and other advantages resulting from itwill be explained in greater detail with reference to preferredembodiments and a number of 20 drawings, in which:

FIG. 1 is a simplified perspective view of a device according to theinvention for the vaporization treatment of samples under reducedpressure in at least one container that can be opened or closed;

FIG. 2 is a partial vertical section of a holder arranged in the heatingarea of the device of FIG. 1 for one or more containers;

FIG. 3 is a simplified perspective front view of a device according tothe invention for the extraction of samples in at least one container bymeans of a solvent at elevated temperature and elevated pressure;

FIG. 4 is a partial vertical section through a holder for the containersarranged in the heating area of the device of FIG. 3, and through thecontainers therein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The main components of the device 1 are a heating device 2, preferablyusing microwaves, with a heating space 3 that can be closed, forexample, by a door, a holder 4 arranged therein with several, preferablyfour or six stand positions 5 for containers 6, a suction pump 7, acondensation-cooler 8 fitted inside the suction pipe 9 leading to thesuction pump 7, several inlet tubes 11 or a common manifold thatbranches into several inlet tubes for a solvent or a gas, for exampleair or an inert gas, and an electronic control device 12, preferablycomprising a computer that operates with predetermined or inputprograms, the control device 12 preferably being associated with akeyboard and a display or VDU for the input of control data. Inaddition, the device 1 is associated with a weighing scale 10 inside oroutside the heating space 3, preferably an electronic weighing scale 10,connected by an electric control lead to the control device 12. Thelatter may be integrated in the device itself, or arranged in thehousing containing the keyboard and the VDU.

The heating apparatus 2 is integrated in a square-shaped housing 13,from the front of which the heating space 3 in the form of asquare-shaped cavity, is accessible and closed off tightly by a shutter,in particular one that swivels upwards. The suction pipe 9 and inlettubes 11 lead through associated openings into the heating space 3. Theholder 4 consists of a material transparent to microwaves, in particulara plastic such as polypropylene, and is a rotating component with alower turntable 14 and an upper turntable 15, between which thecontainers 6 are held. The rotating component can be driven incontinuous rotation or in a back and forth oscillating movement,preferably through approximately 360°. The turntables 14, 15 are solidlyattached to one another by a central, vertical connection piece, in thiscase a connection tube 17, so that they project outwards beyond theconnection tube 17 and form between them a common annular space 18 orindividual spaces to take the containers 6. As shown in particular byFIG. 2, the containers 6, all of the same form, each consist of a pot 23and a flat cover 24, if necessary sealed by an interposed annulargasket. The covers 24 are each held under the upper turntable 15 in avertically flexible way still to be described.

For preference, on the top of the lower turntable 14 and/or theunderside of the cover 24 in the area of each stand position 5, aguideway 19 for the pot 23 is provided, to permit the radial inwardmovement of the pot 23 when it is introduced between the turntable 14and the cover 24. The guideway 19 may be formed of a recess 21 with aflat bottom surface 21a, whose circumferential width is adapted to thewidth of the preferably cylindrical pot 23 and which forms an end-stop Afor the radial inward movement of the pot 23.

The pot 23 of the container 6 consists of several, in the present casetwo parts, namely a lower part 26 and an upper part 27 fitting closelyover its upper rim, at the center of which a space or chamber 28 openingupwards is provided for a sample holder 29. In the present design, thechamber 28 is formed by a vertical cylindrical hole whose bottom isformed by a conical surface 31 converging downwards at an inclination ofaround 45°. The chamber 28 is open at the bottom via a drain channel 32extending downwards, preferably located centrally. The cross-sectionalshape --size and depth of the chamber 28 --corresponds approximately tothat of the size and height of the sample holder 29, so that the lattercan be inserted from above into the chamber 28 with some freedom ofmovement. To be able to take the sample holder 29 out again, the chamber28 has at its top one or more free spaces 33, for example enlargementsof its cross-section, in the area of the upper rim of the preferablypot-shaped sample holder 29, which can be gripped by hand or, forexample, with a pair of tongs.

In the present design, the sample holder 29 comprises a hollowcylindrical circumferential wall 29a and a preferably outwardly convexrounded bottom 29b, and consists of a material permeable to a liquid andtransparent or partially absorbent to microwaves, in particular a filtermaterial, preferably a fibrous glass or plastic material, designedapproximately as a fleece pad and with a wall thickness of around 0.5 to2 mm, especially about 1 mm. In its pot-shaped form, the sample holder29 is strong or rigid enough to be gripped and handled, so that it canbe held without being pressed flat. The diameter of the sample holder 29is about 20 mm, and its height about 40 mm.

The chamber 28 is preferably formed of a thin-walled pot component 34,preferably integrally formed with the top part 27 of the pot. For thispurpose, a flange-shaped radial wall 35 can be used, which rests on therim of the lower part of the pot 26 and surrounds it in order to centerit or engages with it via a projection, particularly an annularprojection 36. To form a seal, between the wall 35 and the free rim 26aan annular gasket is provided, in this case an O-ring 37, which isseated in a circumferential groove of the annular projection 36 andforms a seal between the rim 26a and the wall 35. In the present design,the flange-shaped radial wall 35 with a hollow cylindrical wall portion35a is preferably dome-shaped, with a flat, upwardly-facing supportsurface 35b for the cover 24 above the free rim 26a. By this means,different dome heights can be used not only to achieve adaptationbetween existing pot heights and cover heights, but the volume andheight of the chamber 28 are also enlarged. For preference, on theunderside of the cover 24 or the top side of the upper part of the pot27, a lip seal is provided whose sealing lip 38 is formed in one pieceon the cover 24 or preferably the upper part of the pot 27, and extendsradially outwards with respect to the vertical central axis of thecontainer 6 and is formed by a narrow circumferential groove 38a in thewall 35. The inside space of each container 6 is connected by suctionchannel branches 9a passing through the wall 35 and continuing radiallyinwards in the cover 24, to the common suction manifold 9 extendingoutwards and connected to the cooler 8 and suction pump 7. By unitingthe suction manifold branches 9a, there is produced in that region aso-called rotary connection armature 39 known per se, at the center ofthe holder 4, from which the suction channel branches 9a extendpreferably through sleeves 41 made of an elastic and flexible material,particularly plastic, fitted in corresponding holes of the associatedcover 24 and a component 42 (connection pipe 17) of the holder 4 on theinside thereof for the armature 39.

In a comparable way, the common inlet manifold 11 extends into theheating space 3, and is preferably centrally connected by means of theinlet manifold branches 11a leading from it to the inner space of eachcontainer 6. Both for the suction manifold 9 and for the inlet manifold11 or their branches, a rotary connection armature is needed when theholder 4 is rotated in the sense of a rotor by the drive motor not shownin the figure. When the motion is back and forth, connection hoses thatallow this motion are sufficient.

FIG. 2 shows the course of the inlet manifold 11 with the inlet pipebranches 11a branching off from one section 43 to the containers 6. Theinlet manifold 11 or its branches 11a are used to introduce inparticular a liquid reagent or solvent 44 and/or a flushing gas 45, forexample air or an inert gas. For this, two further inlet pipe branches11b, 11c are used, one of these branches 11b extending from a reservoir46 for the solvent 44 via a pump 46, and the other branch 11c extendingfrom a reservoir (not shown) for the flushing gas, preferably via anon-off and adjustable ventilation valve 47, to the inlet manifold 11.The inlet pipe branches 11a pass through the upper turntable 15 each inthe area of a connection fitting 48, which can also serve as a holdingelement for the cover 24, arranged some distance below the upperturntable 15 and held on it in a vertically elastic flexible way. Thisis achieved by an elastic compression piece 49 arranged between theupper turntable 15 and the cover 24, which guarantees the verticalflexibility of the cover 24 which can be suspended on the upperturntable 15 by means of the connection fitting 48 passing through thecompression piece 49 and into the cover 24. The mouths 11d of thebranches 11a lead centrally into the inner space of the associatedcontainer.

On the top side of the upper part of the pot 27 there is a coaxialgroove or annular recess 50, in whose area the associated suction pipebranch 9a opens into the cover 24 as an angular channel 9b. Within theannular groove 50 are several holes 51 passing through the wall 35 andarranged uniformly around its circumference, in this case four suchholes, which guarantee uniform evacuation of the inner space of thecontainer 6.

The pot components 26, 27 and if necessary also the cover 24 may consistof a material essentially transparent to microwaves such as plastic,glass, quartz or ceramic, or they may consist of a material whichabsorbs microwaves partially, so that during irradiation by themicrowave generator (not shown) they are heated and thereby act asindirect heating elements or auxiliary heating elements to heat thesample material, or to avoid condensation especially in the upper partof the inner walls of the container. For preference, this material willbe a plastic in which particles, especially particles of amicrowave-absorbing material, preferably graphite, are mixed orincorporated. A plastic of this kind is known under the designationWeflon.

In the embodiment shown in FIG. 2, between the container 6 and the lowerturntable 14 there is a pedestal 52 for the pot 23. On the top side ofthe pedestal 52, a plate 53 made of a material that partially absorbsmicrowaves can be placed, for the purpose of additional indirect heatingfrom below. The lower part of the pot 26, with its preferably flatfloor, preferably consists of a transparent material such as glass,quartz or plastic.

In the normal, released position of the cover 24, the vertical distancea between its lower or sealing surface 54 and the lower turntable 14 orthe pedestal 52 is slightly smaller than the height of the pot 43. As aresult, the cover 24 slightly compresses the compression piece 49 whenit rests on the pot 23 after the latter has been pushed in from theside. When pushing the pot in or pulling it out from the side, theconnections of the suction pipe branches 9a and inlet pipe branches 11awith the inner space of the associated container 6 are made (oninsertion) or broken (on extraction) automatically. This makes for easyand rapid handling.

This device 1 is suitable for the drying and/or extraction of samplematerial previously introduced into the sample container 29. In bothcases, during the operation of the device 1 the sample material isheated directly by the microwaves (if the sample material is a microwaveabsorber) and/or indirectly by the heating elements mentioned earlier,and because of the rotation or oscillation of the holder 4, this heatingtakes place uniformly. Vapors given off during the heating are extractedby the suction system from the containers 6, the vapors being flushedout completely by the flow of flushing gas 45. Because of the suction,the pressure in the containers 6 is reduced such that the boiling pointof the liquids to be vaporized, for example water or moisture and/or thesolvent 44, decreases and evaporation is forced and/or can take place atlower temperatures. In addition, the sealing function of the cover 24 isimproved by the suction effect.

The device 1 is set up such that the flushing gas 45 and/or the solvent44 can be admitted to treat the sample, this being adjustable byswitching the pump 46 on or off or varying the pumping rate.

In the working area of an existing laboratory, the device 1 isassociated with a further device 101, with which the sample material canbe extracted under elevated pressure.

The main components of the device 101 are a heating device 102preferably operating by microwaves, with a heating space 103 closed by adoor 103a, a holder 104 positioned in the heating space 103 withseveral, preferably four or six stand positions 105 for pressure vessels106, one overpressure valve 107 for each pressure vessel 106, which whena given inside container pressure (overpressure) is exceeded, opensautomatically and then closes again under the action of an elasticcompression piece, in each case with an adjustment device 108 for eachvalve 107 to preset its elastic prestress level, i.e. to regulate theinternal pressure of the container at which the valve 107 opensautomatically, and a cooling device 110 for each pressure vessel 106,that can be connected to a common supply of coolant 110a, for example acoolant pump 110b, in particular a water pump.

As shown in FIG. 4, the pressure vessels 106 are all of similar designand consist of a pot-shaped housing 109 with a housing floor 111 and ahollow cylindrical, vertically extending housing wall 112. The apertureof the housing, which can be closed off by a cover 113, is limited bythe upper inside rim of the housing wall 112 (FIG. 4).

The valve 107 is positioned in the upper area of the pressure vessel106, its valve component preferably being formed by the cover 113. Whena certain internal pressure in the pressure chamber 106 is exceeded, thevalve 107 opens automatically, so that part of the internal pressure canescape to the outside. This prevents the internal pressure fromexceeding a predetermined value that might overload the pressure vessel106 or cause it to explode.

The valve seat of the valve 107 is formed at the upper inside rim of thehollow cylindrical housing wall 112, and is formed by a conical seatingsurface 107a concentric to the cylindrical housing wall 112 convergingdownwards, and/or a horizontal surface 107c. The cone angle is about 45°to about 75°, preferably approximately 60°. A correspondingly shapedconical sealing surface 107b and/or a horizontal sealing surface 107d isformed in the cover 113 that fits on the housing wall 112 from above.

As shown in FIG. 4, the holder 104 is a rotating component with a lowerturntable 114 and an upper turntable 115, between which the pressurevessels 106 are held. The rotating component can be driven in continuousrotation or in a reciprocating movement, preferably around approximately360°, to ensure uniform heating of the pressure vessels. The turntables114, 115 are solidly connected together by a vertically extendingconnection piece, in this case a connection tube 117, such that theyproject radially outwards beyond the connection tube 117 and form acommon annular space 118 or --when the holder 104 is a round block--individual, radially inwardly-directed spaces to receive the pressurevessels 106. For preference, on the upper side of the lower turntable114 in the area of each stand position 105, a guideway 119 for thepressure vessel 106 is provided, which consists of a radiallyinwardly-extending movement guide with a movement end-stop A tofacilitate insertion of the pressure vessel 106 from the side betweenthe turntables 114, 115. The guideway 119 may be formed by a recess 121with a flat bottom surface 121a, whose circumferential width is adaptedto the width of the preferably cylindrical pressure vessel 106.

As shown in particular by FIG. 4, the adjustment device 108 associatedwith each of the stand positions 105 is formed by an adjustable clampingdevice 123, in particular a clamping screw 124, accessible from aboveand screwed into a threaded hole in the upper turntable 115. An elasticcompression piece 122 is positioned between the pressure vessel 106 andthe turntables 114, 115, preferably on the cover 113 and between thelatter and the clamping screw 124. The compression piece 122 ispreferably formed by a molded piece in the shape of a hollow cone, whichmay be positioned in an opening on top of the cover 113, or acompression disc 122a made of a high-strength material, in particularplastic. The clamping screw 124 is at its upper end provided with agripping element 124a for a turning tool. By setting the clamping screw124 to a corresponding position, the valve 107 can be so adjusted thatit will open and allow the escape of pressure from inside the pressurevessel at any desired value.

Within the scope of the invention it is also possible to position thepressure vessel or vessels not standing, but suspended between theturntables 114, 115, for which purpose a peripheral flange 112a of eachpot-shaped housing 109 is held by a lower turntable 115a with acorresponding radial insertion opening 115b, as illustrated in FIG. 4.With a suspended arrangement of this type, the bottom of the housing 111may be rounded not only on the inside but also outside, in particularforming a hemisphere, whereby less material is needed.

In the standing arrangement of the pressure vessel 106 shown in FIGS. 3and 4 by continuous lines, the housing floor 111 is rounded to form ahemisphere on the inside and is flat or horizontal on the outside, whichrequires the use of somewhat more material.

The pressure vessels 106 are of similar design. In each pressure vessel106, an extractor 125 and a so-termed Soxhlet apparatus 126 isintegrated, as shown.

In greater detail, in the pressure vessel 106 a solvent chamber 127 andover it a sample chamber 128 are arranged, with a vapor duct extendingupwards between the solvent chamber 127 and a vapor space 129 above thesample chamber 128, with a cooling device 110 so arranged in the vaporspace 129 that any condensate 132 of the reagent or solvent produced inthe area of the cooling device 110 will run down into the sample chamber128 and preferably drop on to the sample 133 therein, and with thesample chamber 128 associated with an overflow 134 leading to thesolvent chamber 127.

In the present preferred design, the sample chamber 128 is arranged in asample holder 135 of pot-shaped form made as a separate component, whichcan be inserted from the top into the housing 109 and is supported abovethe solvent chamber 127 to prevent it descending too far down into thesolvent chamber 127. For preference, this is achieved in particular by acentral support bar 136 in the form of a narrow extension of the samplecontainer 135 reaching from its container bottom downwards to the bottom111 of the housing. The sample container 135 has an outer diametersomewhat smaller than the inner diameter of the housing 9, so thatbetween them there is an annular space RS forming the vapor duct 131.The overflow 134 is integrated into the body of the sample container135, i.e. it forms channels passing through the latter, so that no partsof the overflow channel 137 project radially outwards. More precisely,the overflow channel 137 consists of a channel section 137a extendingradially outwards from the bottom area of the sample chamber 128, fromwhich a second channel section 137b extends upwards to the level 138 ofthe sample container 135, a horizontal channel section 137c preferablyextending in the circumferential direction, and a vertical channelsection 137d, with the horizontal channel section 137c, and channelsections 137a and 137d connected together and channel section 137dopening downwards from the body of the sample container 135 preferablyin the form of a tube section 139 extending into the sample containerfrom underneath. The height of the solvent chamber 127 is greater thanthe level b of the solvent 130a, so that the vapor can flow away freely.

For preference, the sample container 135 consists of several individualcomponents enabling the channel sections 137a to 137d to be produced byinjection molding, so that no machining need be done and material cantherefore be used sparingly such as to reduce production costs.

The bottom 135a of the sample container 135 is preferably formedconvergently downwards, particularly in the shape of a hollow cone.

The sample container 135 or its individual components and/or the housing109 can essentially consist of a material transparent to microwaves, inparticular plastic, glass, quartz or porcelain, or of a material whichabsorbs microwaves in part, for which purpose a material transparent tomicrowaves, in particular plastic, in which particles of a material thatabsorbs microwaves are embedded, may be used. A preferred material isplastic in which particles of a microwave-absorbing material, inparticular graphite, are mixed or incorporated, which is known under thedesignation Weflon.

A microwave-transparent material for the sample holder 135 is suitablein cases when the solvent and/or the sample material are substances thatabsorb microwaves, and that will thus be directly heated by themicrowave radiation. If a microwave-transparent material is used as thesolvent and/or sample material, an indirect heating body is needed forthe heating of the sample 133 and/or the solvent, which in the presentcase is formed by the sample container 135 itself which produces thenecessary heat and transfers it to the solvent 130 and the sample 133 inthe sample container 135 and to the solvent 130a present in the solventchamber 127. The heating of the solvent 130a in the solvent chamber 127is important, to contribute to its vaporization, as will be describedbelow. To enhance the heating of the solvent 130a, at least one furthercomponent made of a microwave- absorbing material, preferably alsoWeflon, may be positioned in the solvent chamber 127. In the presentdesign, at least one component, in particular a ring 146, is provided inthe solvent chamber 127 to act as an additional indirect heating body,through which the support bar 136 passes.

To facilitate the insertion and removal of the sample 133, asieve-shaped sample holder 147 in the form of a pot to take the sample133 is provided, which can be inserted from above into the samplecontainer 135. For preference, the bottom of the sieve 147a is roundedor hemispherical, so that the sample 133 will lie in the hollow of thesample holder 147 standing on the bottom 135a, in which the sample willbe moistened even with the residual quantity of the solvent 130 present.The sample holder 147 is preferably of a size such that it projectsbeyond the sample container 135 or up into the area of the space overthe closure ring 135c, where it can easily be gripped from above. Thesample holder 147 consists in particular of plastic, glass or quartz,preferably a fibre material, and may comprise the microwave-absorbingmaterial already described.

It is advantageous to make at least one of the pressure vessels 106,preferably several or all of them, and at least one sample container135, out of a microwave-transparent material and one sample container135 out of a microwave-absorbent material, so that depending on theapplication, the material of the solvent 130 and/or the sample 133, themost appropriate container 135 from the-standpoint of temperaturedevelopment can be used interchangeably.

For preference, the cooling device 110 possesses a cooling body 151arranged at the center of the underside of the cover 113, particularlyin the form of a cooling rod or finger, and which is either convergentat its lower end or of a cross-section only so large as to allow anycondensate formed on it to run down into the sample container 135 and inparticular on to the sample 133. In the present design, a cylindricalcooling body 151 is provided, whose lower end tapers downwards, and inparticular, is hemispherical. The cooling body 151 is connected to acoolant circuit whose coolant may be air or preferably a liquid, forexample water. The cooling body 151 is attached to the cover 113. It istherefore advantageous to connect the inlet and outlet pipes 152, 153for the coolant sideways to the cover 113, such that they pass throughadjacent horizontal channels 154, 155 in the cover 113 and extend as faras the cooling body 151. The vertical channel sections 154a, 155apassing through the cooling body 151 are preferably coaxial, such thatthe cooling body 151 has a hollow cylindrical wall 156 into which a tubesection 157 extends coaxially from above, and whose lower end terminatesshortly above the bottom wall of the cooling body 151 and to whose upperend the inlet tube 152 is connected, while the outlet tube 153 leadsaway from the upper end region of the annular space 158 between thehollow cylindrical wall 156 and the tube section 157.

Around the periphery of the cover 113 there are plug couplings 159, inparticular rapid connection joints, for the connection of hoses 161shown only in FIG. 3, which preferably pass through the housing wall103b of the heating device 102 and are connected to the external pump110b.

All other parts of the pressure vessel 106 including the oscillatingholder 104 and the hoses 161 are made of materials transparent tomicrowaves.

The device 101 operates as follows:

To prepare or extract the sample material in at least one pressurevessel 106 of the device 101, solvent 130 and/or 130a is introduced intothe pressure vessel 106 that has been removed from the holder 104 andopened, and the associated sample 133 is placed in the housing 112 orsample container 135. The housing 109 is then closed by the cover 113and the pressure vessel 106 is replaced in the holder 104 and clamped init, and the connections 161 of the cooling device 110 are established.When the heating space 103 has been closed, the microwave generator isswitched on and for preference, the holder 104 is set into rotation.During the microwave irradiation, the solvent and sample material(sample 133), depending on the material, are heated directly orindirectly by the components (sample holder 135, ring 146) acting asheating bodies, so increasing both the inside temperature in thepressure vessel 106, and the inside pressure as a result of the heatingand evaporation of the solvent 130. The vapor rises up from the solventchamber 127 through the annular gap RS between the sample container 135and the housing wall 112 (vapor duct 131), or through one or moregrooves in the circumferential surface, given that it is prevented fromcooling by heat transfer from the sample container 135. In the vaporspace 129, the vapor precipitates on the cooling body 151 as acondensate and drops into the sample chamber 128 and onto the sample133. When the condensed solvent 130b reaches the level 138 therein, nofurther rise is possible since the solvent 130b flows back through theoverflow 134 into the solvent chamber 127. This is possible owing to thesuction effect of the outlet (137d, 139) leading into the solventchamber 127. In this way, the solvent 130 and 130a can be used in acontinuous cycle, until a given level of saturation has been reached.

In this device 101 and process, extraction takes place in a closedsystem, and not only under excess pressure but also at an elevatedextraction temperature. This results in improved solubility.

In what follows, further advantages of the device 101 or the processcarried out with it will be described.

There is an automatic cycle of the solvent, in which thanks to theelevated pressure and boiling point, better wetting and extraction ofthe sample material is achieved, since the solvent is forced into thesample material by the pressure. For example, the boiling point ofdichloromethane increases from 57° C. at normal pressure to 51° C. atabout 10 bar.

Owing to the closed cycle of the solvent, the consumption of solvent islower, and losses by evaporation outside the system do not take place.

Thanks to the selective heat input (microwave absorption by the solventor synthetic and inert heating elements), the heating time is alsoshort.

Vapors released when the pressure chamber is opened can easily be drawnoff, for example by a suction device connected to the heating space,which avoids vapor concentrations in the workshop. This is particularlyimportant in the case of toxic solvents.

It is therefore evident that the device 1 and the device 101 can beadvantageously used for the vaporization or drying and extraction ofsamples, the device 101 being particularly suitable for extraction.

However, within the scope of the invention it is also possible andadvantageous to use both devices 1, 101 for an extraction process,especially when the sample holders 29, 147 and the chambers 28, 162receiving them are of essentially similar shape and size, so that asingle sample holder B can be used as the sample holder common to bothdevices 1, 101. In such a case, the sample in its sample holder B can beused and treated in both devices.

Below, an example of such a process for the extraction and drying of asample will be described. The sample, for example cheese, is introducedinto the sample holder B and weighed. The sample holder B is then placedin the holding chamber 28 of a container 6, and the latter is pressedinto the holder 4. A drying process is then carried out in device 1 byheating with microwaves as described above, during which the vapors areextracted and an underpressure produced thereby, which accelerates thedrying.

As the next step, for example, the fat content of the dry mass isestablished by dissolving out the fat. For this extraction, the sampleholder B with its sample material is removed from the container 6,inserted into the chamber 162 of a pressure vessel 106 of the device 101with the housing 109 open, the pressure vessel 106 is closed andinserted into the holder 104 of the device 101, and the latter is setinto operation, whereby the sample is heated as described above andextracted under excess pressure and at an elevated temperature. Suitablesolvents are, for example, hydrocarbons.

At the end of this extraction step, the sample holder B with theextracted sample material is removed from the pressure vessel 106 oncethe latter has been taken out of the device 101 and opened, and with thepump 46 turned off or disconnected, i.e. without any input of solvent44, dried once more to remove solvents from the sample residue. At theend of the new drying process, the sample holder B with the extractedand dried sample residue is removed and weighed again, to establish thefat content.

Any transport of a sample between various treatment steps in variouscontainers or devices involves the risk of contamination or loss ofparts of the sample, and necessarily leads to errors. This disadvantageis avoided by the process according to the invention, since one and thesame sample container B is used in both devices 1 and 101.

I claim:
 1. A process for the extraction of samples by means of avolatile solvent, said process comprising the steps of:placing thesample in a sample holder in a container of a first device, heating thesample and the volatile solvent, whereby extraction takes place in theclosed container under elevated pressure, wherein said process includesthe steps of:transferring the sample with its sample holder into asecond device, said second device comprising a container into which thesample holder also fits, drying the sample in the container of thesecond device, and drawing off the vapors so produced, whereby there isproduced an underpressure in the container of the second device.
 2. Aprocess according to claim 1, wherein,before causing extraction in thefirst device, drying the sample by heating it in the container of thesecond device, drawing off the vapors so produced, and thereby producingan underpressure in the second container.
 3. Apparatus for carrying outa process according to claim 1 or 2, said apparatus comprising,a firstdevice which includes, at least one container, a microwave heater havinga container holder for holding the container in a heating space, areceptacle chamber within the container for a volatile medium, saidcontainer having a sample holder for holding the sample in saidreceptacle chamber, whereinthe first device is associated with a seconddevice for the evaporation and drying of the sample in at least onesecond device container, in that the second device comprises a heatingchamber that is heated by microwaves, a suction device with a suctionmanifold and an inlet device with an inlet manifold for a gas, in thatthe suction manifold and the inlet manifold are connected to the insidespace of the second device container, and in that the containers of thefirst and second devices are so designed that the same sample holder canfit into both of them.
 4. Apparatus according to claim 3 whereinthefirst device comprises at least one pressure vessel includinga firstchamber to receive the volatile solvent, a sample container positionedhigher than the first chamber, and having a second chamber to receive asample, at least one heating element of microwave-absorbent material toheat the volatile solvent, and the heating element being positioned inat least one of the first and second chambers.
 5. Apparatus according toclaim 3 whereinthe first device comprises at least one pressure vesselincludinga first chamber to receive the volatile solvent, a samplecontainer positioned higher than the first chamber, and having a secondchamber to receive a sample, at least one heating element ofmicrowave-absorbent material to heat the volatile solvent, and theheating element forming the second chamber.
 6. Apparatus according toclaim 3 whereinthe first device comprises at least one pressure vesselincluding,a first chamber to receive the volatile solvent and a samplecontainer positioned higher than the first chamber, and having a secondchamber to receive a sample, said first device including a closeableheating space to receive the pressure vessel, said pressure vesselcomprising a pot-shaped housing with a cover made of amicrowave-transparent material that rests freely on the housing, saidpressure vessel also forming the first chamber, and the inner surface ofthe bottom of the pressure vessel being rounded to form a hemisphere. 7.Apparatus according to claim 3, wherein the first device comprises atleast one pressure vessel includinga first chamber to receive thevolatile solvent, a sample container positioned higher than the firstchamber and having a second chamber to receive a sample, a vapor ductconnecting the first chamber with the second chamber, an overflow ductconnecting the second chamber with the first chamber, and a coolingdevice for a vapor space positioned over the sample container, and inthat the sample container comprises a pedestal which projects into thefirst chamber, and in that at least one of the sample container and thepedestal is comprised at least in part of one of a microwave-transparentand a microwave-absorbing material.
 8. Apparatus according to claim 3,wherein the first device comprises at least one pressure vesselincludinga first chamber to receive the volatile solvent, a samplecontainer positioned higher than the first chamber and having a secondchamber to receive a sample, a vapor duct connecting the first chamberwith the second chamber, an overflow duct connecting the second chamberwith the first chamber, and a cooling device for a vapor spacepositioned over the sample container, and in that the sample containercomprises a pedestal which stands on the bottom of the first chamber,and in that at least one of the sample container and the pedestal iscomprised at least in part of one of a microwave-transparent and amicrowave-absorbing material.
 9. A device for the extraction ofcomponents from samples by means of a volatile solvent, in at least onepressure vessel, said device comprising:a pressure vessel whichincludes:a first chamber for receiving the volatile solvent, a samplecontainer higher than the first chamber with a second chamber forreceiving a sample, and at least one heating element of microwaveabsorbent material provided in the pressure vessel, wherein,the heatingelement is positioned within at least one of the first and secondchambers.
 10. A device according to claim 9 whereinthe heating elementis formed by a pedestal of the sample container wherein the pedestalconsists of a microwave-absorbing material and projects into the firstchamber.
 11. A device according to claim 10, wherein,said pedestalstands on the bottom of said first chamber.
 12. A device according toclaim 9, wherein,at least one of the heating element and the samplecontainer consists at least in part of plastic.
 13. A device accordingto claim 9, wherein,said heating element consists at least in part ofplastic.
 14. A device according to claim 10, wherein,at least one of thesample container and the pedestal consists at least in part of plastic.15. A device according to any of claims 9, 10, 11, 12, 13, or 14,wherein,the sample container consists of a microwave-absorbent material.16. A device according to any of claims 10, 11, 13 or 14, wherein,thepedestal is formed by a bar projecting downwards.
 17. A device accordingto claim 15, wherein,the pedestal is formed by a bar projectingdownwards.
 18. A device according to any of claims 10, 11, 12, or 13,wherein,the heating element is formed by a ring.
 19. A device accordingto claim 16, wherein,the heating element is formed by a ring and in thatthe ring encircles the bar.
 20. A device according to claim 17,wherein,the heating element is formed by a ring and in that the ringencircles the bar.
 21. A device according to any of claims 10, 11, 13and 14, wherein,the pedestal is formed by a bar projecting downward andin that the heating element is formed by a ring which encircles the bar.22. A device according to claim 19, wherein,the sample containerconsists of a microwave-absorbent material.
 23. A device according toclaim 20, wherein,the sample container consists of a microwave-absorbentmaterial.
 24. A device according to claim 21, wherein,the samplecontainer consists of a microwave-absorbent material.
 25. A deviceaccording to any of claims 9, 10, 11, 12, 13 or 14, wherein,that thechamber to receive the volatile solvent is positioned in the bottom areaof the pressure vessel.
 26. A device according to claim 10, wherein,thesample container consists of a microwave-absorbent material.
 27. Adevice according to claim 10, wherein,the pedestal is formed by a barprojecting downwards.
 28. A device according to claim 27, wherein,theheating device is formed by a ring.
 29. The device according to claim 27wherein the heating element in the first chamber is a ring.
 30. A deviceaccording to claim 10, wherein,the pedestal is formed by a barprojecting downward and in that the heating element is formed by a ringwhich encircles the bar.